1. Field of the Invention
The present invention relates to device for transmitting electrical signals to or receiving electrical signals from a human patient. In particular, the present invention relates to a transcutaneous electrode device for electrical connection to an anatomical site which is covered by a cast.
2. Description of the Prior Art
Medical electrodes which are attached to the skin of a patient have been used for many years. With the ever-increasing sophistication of medical electronics, medical electrodes are continually finding new and wider uses. One type of medical electrode may be termed a "monitoring" electrode, which is used in conjunction with monitoring equipment such as electrocardiograph and electroencephalograph equipment.
Another common type of medical electrode may be termed a "transmitting" or "stimulating" electrode. This type of electrode is used with a transcutaneous electrical stimulator to apply electrical current to the patient's body for treatment of pain, muscle stimulation, or the regeneration of tissue.
There are instances when it would be advantageous to apply either a monitoring or a transmitting electrode to a patient's skin, but that site is covered by an intervening plaster or synthetic cast, because the patient has one or more fractured bones. For example, the application of transcutaneous electrical nerve stimulation can relieve pain associated with the fracture, or can prevent muscle atrophy in a portion of the body which is covered by the cast. In other cases, the application of electrical current to the patient's skin can be used to stimulate regneration of bone tissue at the fracture site.
In the prior art, the application of an electrode to a site covered by a cast has required "windowing" of the cast by cutting the hardened cast with a cast saw. A conventional monitoring or transmitting electrode is then placed in direct contact with the skin and is connected to a monitoring device or a stimulator. This procedure has significant disadvantages.
First, although cast saws have been developed that are generally quite safe, small abrasions or cuts of the patient's skin can still occur during the windowing procedure.
Second, the windowing can result in structural weakness of the cast.
Third, in some cases the particular area of the body does not allow for windowing at all. This can be due to the nature of the fracture or the location of the fracture. For example, the electrical current may be required to be applied directly to the fracture site, which is generally the least desirable place to cut a window in the cast.
Fourth, it is often difficult to apply and remove the electrodes through the window without bothering either the cast or the area of the body which is covered by the cast.
Fifth, in order to maintain contact with the skin, the electrode typically must have an adhesive layer. As a result, the electrode leaves a residue on the skin which is difficult to clean through the window.
There is a continuing need for an improved device and method for transmitting and receiving electrical signals from the skin at an anatomical site which is covered by an intervening cast. In particular, there is a need for a device which is simple in construction, simple to use, and maintains the structural integrity of the cast, while permitting reliable electrical contact to the patient's skin.